Engineering the structures of nanoporous clays with micelles of alkyl polyether surfactants

Composite clay nanostructures (CCNs) were observed in intercalating Laponit e clay with alumina in the presence of alkyl polyether surfactants which co ntain hydrophobic alkyl chains and ether groups. Such nanostructured clays are highly porous solids consisting of randomly orientated clay platelets i ntercalated with alumina nanoparticles. The pores in the product solids are larger than the dimension of the surfactant molecules, ranging from 2 to 1 0 nm. This suggests that the micelles of the surfactant molecules, rather t han the molecules, act as templates in the synthesis. Interestingly, it is found that the size of the framework pores was directly proportional to the amount of the surfactants in terms of moles, but shows no evident dependen ce on the size of the surfactant molecules. Broad pore size distributions w ere observed for the product CCNs. This study demonstrates that introducing surfactants in the pillaring process of clays is a powerful strategy for t ailoring the pore structures of nanoporous clays. With this new technique, it is possible to design and engineer such composite clay nanostructures wi th desired pore and surface properties by the proper choice of surfactant a mounts and preparation conditions.